Piston pump having a cylinder barrel

ABSTRACT

A piston pump for delivering fluids includes a piston configured to be driven to perform a reciprocating stroke movement. The piston pump includes a cylinder barrel in which the piston is held in an axially displaceable manner. The piston pump also includes a displacement chamber which is arranged in the cylinder barrel between an inlet valve and an outlet valve. The outlet valve is arranged on a cylinder barrel base, and, on a side of the cylinder barrel base which faces away from the displacement chamber, an annular projection is formed. The annular projection is configured to surround an installation space for the outlet valve.

STATE OF THE ART

The invention relates to a piston pump for delivering fluids, having apiston which can be driven to perform a reciprocating stroke movement,and a liner in which the piston is received so that it is axiallydisplaceable, and a displacement chamber arranged in the liner betweenan inlet valve and an outlet valve, wherein the outlet valve is arrangedon a liner base.

Piston pumps of various designs are known. They are used in motorvehicles having vehicle hydraulic brake systems. The known piston pumpscomprise an inlet valve, an outlet valve and a displacement, working ordelivery chamber, which is arranged between the inlet valve and theoutlet valve. The displacement chamber is arranged in a pump cylinder,which here forms a liner and is usually of a substantially cup-shapeddesign. A passage opening, which is opened and closed by the outletvalve, is formed in a liner base of the pump cylinder. Here the outletvalve, which is usually embodied as a non-return valve, is arranged inan outlet valve cover, which is mounted externally on the liner. Anoutflow into a delivery line, into which the then pressurized fluid,especially the brake fluid, is discharged, is furthermore formed in theoutlet valve cover.

In the brake system the piston pump serves, for example, to return brakefluid from a wheel brake cylinder or from a plurality of wheel brakecylinders into a brake master cylinder and/or to deliver brake fluidfrom a reservoir into a wheel brake cylinder or into a plurality ofwheel brake cylinders.

The piston pump is needed in vehicle brake systems with wheel slipcontrol (ABS or ASR), a traction control system (TCS) and/or in a brakesystem serving as a steering aid (FDR) and/or in an electro-hydraulicbrake system (EHB) or an electronic stability program (ESP).

DE 10 2006 027 555 A1 discloses a piston pump for delivering fluids,having a piston, a cylinder element and a delivery chamber arrangedbetween an inlet valve and an outlet valve, wherein the outlet valvecomprises a closing member, a pre-tensioning device and a disk element.The outlet valve is arranged in a cover and an outflow into a deliveryline ensues via this cover. A sealing seat of the outlet valve isarranged on the disk element.

On opening of the outlet valve, unwanted noises can occur due todimensional tolerances of the individual components. Efforts aretherefore underway to optimize just such piston pumps as these, actingas ABS, ASR or ESP pump elements, with regard to their noise emissionsand to improve the assembly of the individual sub-assemblies of suchpiston pumps.

DISCLOSURE OF THE INVENTION

According to the invention a piston pump is created for deliveringfluids, having a piston which can be driven to perform a reciprocatingstroke movement, and a liner, in which the piston is received so that itis axially displaceable, and a displacement chamber arranged in theliner between an inlet valve and an outlet valve, wherein the outletvalve is arranged on a liner base. An annular extension of the liner,which encloses an installation space for the outlet valve, is formed onthe side st of the liner base remote from the displacement chamber.

According to the invention two functional units are combined in onesingle liner, that is to say a displacement chamber on the one hand andthe fitting space for the outlet valve on the other. This simplifies theassembly of the inventive piston pump of a vehicle hydraulic brakesystem and also creates further space for damping measures or for adevice used for damping.

This measure also makes it possible to reduce the dimensional tolerancesof the components, and therefore to reduce the noise generated.

The hydraulic piston pump comprises a cylindrical piston, which in aliner of substantially cup-shaped design is supported so that it can berun into and out of a cylinder bore. The liner is inserted, inparticular, into a cylinder bore of a pump housing of the piston pump ina hydraulic unit. Inside the cylinder bore of the liner a fluid-filleddelivery area or delivery chamber is provided between an inlet valve andan outlet valve. When the piston runs out of the cylinder, a vacuum isbuilt up in the delivery area and the piston sucks fluid into thedelivery area via the inlet valve. When it runs in on the other hand,the piston displaces the fluid out of the delivery area via the outletvalve into the hydraulic system for performing work. A passage opening,which is opened and closed by the outlet valve, is formed in the base ofthe liner.

The outlet valve comprises a closing member, which is advantageouslyembodied as a ball or plate. The liner is preferably combined with anannular extension or the latter is subsequently formed onto the liner asa hollow cylindrical continuation on the liner, in order to thenaccommodate the outlet valve inside the hollow cylindrical continuation.This has the advantage that components such as the closing member, thespring and noise damping means can be arranged inside the hollowcylindrical continuation from the outlet valve-side, as part of a simpleassembly process, which is performed in the opposite direction to theusual one.

Here the outlet valve, which is preferably embodied as a non-returnvalve, is arranged in the part of the extension joined onto the liner,and an outflow into a delivery line of an associated pump housing isfurthermore formed in the extension. The outflow is advantageouslyformed by means of a circumferential recess and a radial duct. Thecircumferential recess is preferably formed on the liner on the sideremote from the displacement chamber, and the radial duct preferablyconnects the installation space of the outlet valve to the recess. Theoutlet valve here advantageously comprises the closing member, apre-tensioning device for pre-tensioning the closing member and a baseelement for supporting the pre-tensioning device.

Here the liner of the piston pump may be of longer design dimensions,thereby additionally affording further space in the area of the outletvalve for any damping measures.

A closure element in the form of a closure cap is advantageouslyattached to the annular extension. The closure element is advantageouslycaulked into the liner and for its part caulked in the pump housingitself. Alternatively the closure element may also just be attached tothe extension of the liner and caulked only in the pump housing, inorder to create a fluid-tight and force-absorbing positional safeguardfor the closure element in this area. Overall the closure element isintegrated into the liner and the two combined with one another to formone unit, so that unwanted noises due to opening of the outlet valve arethereby already reduced.

The integrated closure element, which is preferably designed as anoutlet valve cover or as an integrated closure cap of the outlet valve,is preferably made from aluminum. This affords external protectionagainst corrosion and secure caulking in the pump housing. The aluminumhas a ductility such that the caulking of the closure element in thehousing wall of the liner can easily be achieved by positive interlockand frictional connection.

An exemplary embodiment of the solution according to the invention isexplained in more detail below with reference to the schematic drawingsattached, of which:

FIG. 1 shows a longitudinal section of a piston pump according to theinvention, having a liner and a closure element in the associated pumphousing and

FIG. 2 shows a perspective view of the liner together with a closureelement of the piston pump according to FIG. 1.

FIG. 1 represents a piston pump 10, which comprises a stepped cylinderbore 12 in a hydraulic unit, which forms a pump housing 14. Thehydraulic unit, of which only a fragment surrounding the piston pump 10is represented in the drawing, is an integral part of a vehiclehydraulic brake system with wheel-slip control, not represented further.Besides the piston pump 10, further hydraulic components such assolenoid valves or pressure accumulators are incorporated therein andare hydraulically connected to one another and to the piston pump 10according to the invention.

The piston pump 10 comprises a piston 16, one end of which, remote fromthe displacement chamber 18, is guided in the pump housing 14 by a firstguide ring 20 and sealed off by a sealing ring 22. The other end of thepiston 16, facing the displacement chamber 18, is guided in a liner 26of the piston pump 10 by a second guide ring 24 and sealed off by asealing ring 28. The liner 26 is inserted with a press fit into thecylinder bore 12 of the pump housing 14. The press fit produces a sealbetween the inlet side and the outlet side, that is to say between thelow-pressure side and the high-pressure side of the piston pump 10.

For the pump inlet an axial blind bore 30, which is crossed bytransverse bores 32 close to its base, is fitted in the piston 16 from aside facing the displacement chamber 18. Through windows 34 in aperipheral wall 36 of the liner 26, the blind bores and transverse bores30, 32 communicate with an admission bore 38, which is inserted in thehydraulic unit forming the pump housing 14 radially to the piston pump10.

At the displacement chamber end of the piston 16, a non-return valve isfitted as inlet valve 40. As valve closing member the inlet valve 40comprises a valve ball 42, which interacts with a tapered valve seat 44,which is inserted at an orifice of the blind bore 30 of the piston 16. Ahelical compression spring as valve closing spring 46 presses the valveball 42 against the valve seat 44. The valve ball 42 and the valveclosing spring 46 are accommodated in a valve housing 48, which is madefrom sheet metal as a cup-shaped deep-drawn part having a diametercorresponding approximately to the diameter of the piston 16, and isprovided with flow passage openings 50. The valve housing 48 has anannular step 52, with which it bears on an end face of the piston 16facing the displacement chamber 18. It comprises an integral, externallyprojecting radial flange 54, against which a helical compression springserving as piston return spring 56 presses and in this way holds thevalve housing 48 on the piston 16. At the same time the radial flange 54retains the guide ring 24 and the sealing ring 28 between it and asupport ring 60, resting on an annular shoulder 58 of the piston 16, onthe piston 16 in an axial direction.

Via the radial flange 54 of the valve housing 48, the piston returnspring presses the piston 16 in an axial direction against an eccentric62, which can be driven by an electric motor and which serves fordriving the piston 16 to perform a reciprocating stroke movement in aknown manner.

On a displacement chamber side the liner 26 comprises an integral linerbase 64, in which a central through-hole 66 is inserted for the pumpoutlet. The liner 26 is extended beyond this liner base 64 by a hollowcylindrical portion or annular extension 67 on its side remote from thedisplacement chamber 18. The annular extension 67 comprises aninstallation space 69, integral with the liner 26, for an outlet valve72, which can be fitted in this installation space 69 on the liner 26 inreverse order.

Adjoining the annular extension 67 is a closure element 68, which hasthe form of a closure cap, which is integrated into the annularextension 67 by pressing in a step 73, and in so doing is inserteddirectly into the cylinder bore 12. The closure element 68 is positivelyconnected by a caulking 70 to the pump housing 14 and sealedfluid-tightly. The closure element 68 is thereby additionally alsosecured in the liner 26.

The closure element 68 is preferably formed from aluminum. This ensuresexternal protection against corrosion and owing to the ductility of thealuminum affords a secure connection through the caulking 70 of theclosure element 68 in the pump housing 14.

The outlet valve 72 is designed with a spherical closing member 74 and areturn spring 76 as pre-tensioning device, and a damping device 78 assupport and base element for the return spring 76. The return spring 76exerts a return force on the closing member 74, so that this is pressedin the direction of the central hole 66.

The liner 26 has a radial duct 79 passing through it, which leads to anannular recess 80, in particular an annular duct, formed on the outsidethereof, for the fluid to flow out of the pump housing 14 through anoutflow duct 82 when the outlet valve 72 is opened.

In its longitudinal extent, therefore, the liner 26 is of extendeddesign in order to afford additional space in conjunction with theintegrated closure element 68. Due to the integrated arrangement of theannular extension 67 in the form of a sleeve extension and the caulkingof the closure element 68 directly in the liner 26, however, the overalllength of the piston pump 10 is not necessarily extended.

The design of the piston pump 10 according to the invention with theliner 26, the annular extension 67 and the integrated closure element 68allows the closing member 74, the return spring 76 and the dampingdevice 78 to be easily fitted from the outlet valve-side. The liner 26itself is machined during manufacture. The machining according to theinvention for producing the liner 26 with the hollow cylindrical portionand the annular extension 67 is therefore not only feasible but alsocost-neutral. In addition, the design according to the invention affordsadditional space for the installation of the damping device 78.

FIG. 2 shows an external view of the liner 26 with the annular extension67 extended thereon and the integrated closure element 68.

Also externally visible are the recess 80 for the outflow of fluid,which passes from inside the delivery chamber into the recess 80 throughthe radial duct 79 (not shown here).

All features represented in the description, the following claims andthe drawings may be essential for the invention, both individually andin any combination with one another.

1. A piston pump for delivering fluids, comprising: a piston configuredto be driven to perform a reciprocating stroke movement; a linerconfigured to receive the piston such that the piston is axiallydisplaceable; a displacement chamber arranged in the liner between aninlet valve and an outlet valve; and a liner base, wherein the outletvalve is arranged on the liner base, and wherein an annular extension ofthe liner is configured to enclose an installation space for the outletvalve, the annular extension formed on a side of the liner base that isremote from the displacement chamber.
 2. The piston pump as claimed inclaim 1, further comprising a circumferential recess formed on the sideof the liner base that is remote from the displacement chamber.
 3. Thepiston pump as claimed in claim 2, further comprising a radial ductconfigured to connect the installation space to the circumferentialrecess, the radial duct formed in the liner.
 4. The piston pump asclaimed in claim 1, further comprising a closure element configured as aclosure cap, the closure element attached to the annular extension. 5.The piston pump as claimed in claim 4, wherein the closure element ismade of aluminum.
 6. The piston pump as claimed in claim 4, wherein theclosure element is produced by machining.
 7. The piston pump as claimedin claim 4, wherein the outlet valve includes: a closing member; apre-tensioning device; and a base element configured to support thepre-tensioning device.
 8. The piston pump as claimed in claim 7, whereinthe closing member is a ball.
 9. The piston pump as claimed in claim 7,further comprising a space configured to accommodate a damping device,the space arranged between the closing member and the closure element.